Feeding a summer house

[costanza]

Bit of help if you wouldnt mind guys.

I need to run a 40m cable to a summer house in a customers garden. The summer house will only have two sockets and only be used for maybe plugging in a lamp.

The best way to feed it will obviously be straight from the consumer unit. However, he has an outside socket that he would like to use as the feed. Is this possible? I know fused spurs are unlimited...but does this come under that category? The summer house will have its own 4-way consumer unit and therefore fused. Maybe even RCD if neccessary.

What do you think?

 

[IQ Electrical]

Have a quick look at this:

 

[tanglewood]

Hi, Where is the socket fed from ? if its a spur itself you will have to install a fused spur next to it, then onto summerhouse. Only gives you 13a, if you think thats enough then there you go. Other option is from CU or split incoming supply into tails block, take L/N to summerhouse CU and use earth spike at summerhouse, gives you more options this way, as you never know what people will try and plug in or use in the future. You will also need to do volt drop calculation due to length of run, if it was me i would stick in a 10mm SWA and use a 40a/30Ma RCD at CU. Difference in cost between 6mm and 10mm cable,not much.

 

[cadspark]

Is the outdoor socket currently a spur from a socket in the house?
Is it already RCD protected from house?

If yes to both the above you can add an IP rated FCU before the outside socket and feed into that and then come from that socket to your supply to the summerhouse. You won't need an RCD in there if you already have RCD protectio from the house CU.

 

[costanza]

The house is RCD protected. I fear that the outside socket is itself already a spur. I havent seen it yet though.

It crossed my mind that i could put a 4-way CU where the outside socket is now. From there i could run my SWA to the summerhouse. Also next to the CU i could put a socket for them as he doesnt want to lose that one.

All very farcical but the house CU is a further 40m run at least.

All suggestions are very much appreciated

 

[tanglewood]

Its hard to give advice when the subject is a bit vague. Have you given a price for this job ? You must have done a site visit to know the house is RCD protected. Did you check the options for power supply to summerhouse befors leaving ? also, if the socket is a spur, how far away is it fed from ? and what size cable ? you have to add in this plus the 40m run to summer house if you are going to swap the socket for a 4way consumer unit, which i would not advise (IP ratings, nuisance tripping in house, etc etc) so YOU could end up with a feed to summerhouse which , from the origin of supply (probably 2.5mm cable) is 40m + (what size cable do you think you could use to supply summerhouse from "new" CU??? bigger or smaller?

 

[costanza]

It's my girlfriends parents house so i have some knowledge of the building. Your point about taking into consideration the existing length of the ring final circuit is a good one. It is definitely under 100m though.

The outside socket (im pretty sure) is a spur. Its fed from a socket within the ring that is on the other side of the wall. Its a 2.5 cable. Even if i was to use 6mm cable i guess there is no getting away from the fact that that im adding 40m to essentially a 2.5mm circuit.

The more i write about, the more sensible (although costly) it seems to run from the house's CU

 

[tanglewood]

If youre gonna do it do it right ! especially as its your girlfriends parents house !!

 

[costanza]

Good plan! Cheers for your advice

 

[Amp David]

Post #2 here here!!!

Why are feeds to outbuilding so hard to design?

 

[tanglewood]

Good link #2, but still only 13a to summerhouse. SUMMERHOUSE ! somebody plugs in a 3kw patio type heater when it gets a bit chilly after their barbie, out go your lights, off goes your music, scrabble around for a 13a fuse in the dark while probably half cut, over goes patio heater, chaos ensues, end to perfect evening, just needs a little thought is my opinion!

 

[IQ Electrical]

Good link #2, but still only 13a to summerhouse. SUMMERHOUSE ! somebody plugs in a 3kw patio type heater when it gets a bit chilly after their barbie, out go your lights, off goes your music, scrabble around for a 13a fuse in the dark while probably half cut, over goes patio heater, chaos ensues, end to perfect evening, just needs a little thought is my opinion!

I take your point but you design and quote to your client's requirements and BS7671:2008 compliance.